HTML <canvas>: add WEBP lossless encoding support

third_party/WebKit/LayoutTests/fast/canvas/toDataURL-supportedTypes.html

Index: third_party/WebKit/LayoutTests/fast/canvas/toDataURL-supportedTypes.html
diff --git a/third_party/WebKit/LayoutTests/fast/canvas/toDataURL-supportedTypes.html b/third_party/WebKit/LayoutTests/fast/canvas/toDataURL-supportedTypes.html
index 02475d8e8c74eb362bdd6c2b29fc1cec7c183a35..bcfff47f37b914e182b6d539f140dbe865d11587 100644
--- a/third_party/WebKit/LayoutTests/fast/canvas/toDataURL-supportedTypes.html
+++ b/third_party/WebKit/LayoutTests/fast/canvas/toDataURL-supportedTypes.html
@@ -25,7 +25,7 @@
         var supportedMIMETypes = [
             "image/png",
             "image/jpeg",
-            "image/gif",

[urvang, 2016/05/03 17:28:19]

GIF is not supported?
If so, this should ideally be a separate patch.
Or at least, this should be mentioned in the patch description.

[Noel Gordon, 2016/05/04 00:43:18]

Nope.  There has never been a toDataURL("image/gif") encoder in Blink, nor in
WebKit iirc.
Done, noted in change description.

+            "image/webp",
         ];
 
         function testToDataURL()
@@ -41,6 +41,7 @@
             testMIMEType(undefined);
 
             // Test other formats that we don't support
+            testMIMEType("image/gif");
             testMIMEType("image/x-webkitbitmap");
         }